My thinking is that it's a lot easier on the logistics of fast delivery times. When someone comingles inventory with Amazon it means someone else paid the initi

My thinking is that it's a lot easier on the logistics of fast delivery times. When someone comingles inventory with Amazon it means someone else paid the initial shipping cost from manufacturer to Amazon warehouse. It could even be in Amazon's best interest (on paper only, thus the quality issues) to preferentially ship the commingled inventory before dipping into their direct purchases to maximize profit per sale by reducing pressure on Amazon itself to keep their inventory topped off, since, as I'd bet any business owner that sells physical product can tell you, money tied up on warehouse shelves is not doing you any good.